In an ordinary open-end spinning machine, a fiber bundle, fed by a fiber bundle feed device such as a feed roller, is liberated into individual fibers by an opening device such as a combing roller. The liberated individual fibers are fed into a spinning rotor and deposited on a ring shaped accumulation wall of the spinning rotor, so that a ring shaped fiber bundle is continuously formed on the accumulation wall of the spinning rotor. Then, the bundle of fibers is separated from the above-mentioned ring shaped fiber bundle while imparting twist to the bundle of fibers by the high speed rotation of the spinning rotor and, consequently, a twisted bundle of fibers, that is a yarn, is created. The yarn is taken from the spinning rotor via a guide tube by means of a drawing off mechanism composed of a draw-off roller and a top roller driven by frictional contact with the draw-off roller. The yarn is formed on a bobbin which is rotatably mounted on a winding roller by the principle of frictional contact, so that a yarn package such as a cheese is formed on the bobbin.
In the above-mentioned open-end spinning machine, an apparatus for controlling the driving of the driving elements at the time of starting or stopping the spinning operation has been utilized. That is, the starting or stopping of the driving of the driving members towards the normal direction or the reverse direction, etc., are carried out in a controlled condition with appropriate timing in connection with other driving members according to the controlled signals issued from the control apparatus. As a result the spinning operation is carried out under good conditions. For example, at the time of starting the machine, the rotary spinning chamber or the like is actuated and, simultaneously, the draw-off roller and winding roller are rotated in a reverse direction. Consequently, the end of the yarn wound on the bobbin in the form of a cheese is fed back to the interior of the rotary spinning chamber through the guide tube. After the lapse of a certain period of time from the start of the reverse rotation of the draw-off roller and winding roller, the fiber bundle feed device is actuated by a timer or the like mounted in the control apparatus to feed liberated fibers into the spinning rotor. By another timer or like means mounted in the control apparatus, after the lapse of a certain period of time from the start of the reverse rotation of the draw-off roller and winding roller, the rotation direction of these rollers is changed over from the reverse direction to the normal direction, and the yarn piecing operation is performed in the rotary spinning chamber.
When the operation of the machine is stopped, in order to perform the yarn piecing operation assuredly at the start of the spinning operation of the subsequent cycle after the lapse of a certain period of time from the stopping of the device for feeding a bundle of fibers when the driving motor of the open-end spinning machine is stopped, the rotation of the draw-off roller and the winding roller are controlled so as to be able to stop in such a condition that the yarn end is retained in the guide tube. The above-mentioned time control is carried out by utilizing timers or like means disposed in the control apparatus.
With advance of the winding operation, the quantity of the yarn wound on the package increases. Since a slip between the yarn package and the winding roller at the time of the starting or stopping increases in accordance with the change of the weight of the yarn package, operational timings of the respective driving members set to be actuated at predetermined time intervals become upset and it becomes impossible to maintain good spinning conditions. That is, since the timing of delayed initiation of the feeding of fibers and the timing of delayed changeover of the rotation direction of the draw-off roller and winding roller from the reverse direction to the normal direction are set in predetermined conditions respectively by a timer or like means, when the reverse rotation of the draw-off roller and winding roller is started, a large force of inertia is imposed on the yarn package, because the quantity of the yarn wound on the yarn package has become large, and a slip is caused between the yarn package and winding roller. Owing to this slip, the rotation of the yarn package is started later than the rotation of the winding roller and, therefore, the contact timing between the end of the yarn fed back to the spinning rotor and the fibers fed to the spinning rotor from the opening device becomes upset. Further, when the rotation direction of the draw-off roller and winding roller is changed over from the reverse direction to the normal direction, a large force of inertia acts on the yarn package because the quantity of the yarn wound on the yarn package has become large. Therefore, owing to a slip caused between the yarn package and the winding roller, the rotation direction of the yarn package is changed over to the winding direction (normal direction) at a time later than the change of the rotation direction of the winding roller. Accordingly, the timing of drawing out the yarn from the spinning rotor becomes upset and the ratio of success in the yarn piecing operation is remarkably reduced. This is a first defect involved in the conventional control apparatus of the open-end spinning machine.
Since the timing of delayed stopping of the draw-off roller and winding roller is set with regard to predetermined constant conditions respectively by the timer or like means, as mentioned hereinbefore, when the driving of the draw-off roller and winding roller are abruptly controlled and stopped, a large force of inertia is imposed on the yarn package because the quantity of the yarn wound on the yarn package has become large and a slip is caused between the cheese and winding roller. Owing to this slip, the tension on the yarn is drastically increased between the yarn package and the nip point of the draw-off roller and the top roller, so that the yarn is possibly broken. Naturally, such yarn breakage renders the yarn piecing operation difficult at the start of the spinning operation of the subsequent cycle. This is another defect involved in the conventional control apparatus of the open-end spinning machine.